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DEPARTMENT OF EARTH AND ENVIRONMENTAL SCIENCES 106 GEOSCIENCE, L-DEO COLUMBIA UNIVERSITY

TO: FACULTY, GRADUATE STUDENTS , AND RESEARCH STAFF FROM: MISSY PINCKERT RE: ANNUAL DISSERTATION TOPIC LIST (ORALS PASSED THROUGH SPRING ´10) DATE: 8/10/10

NAME DATE ORALS PASSED ADVISORY COMMITTEE

KAT ALLEN 3/10 Hoenisch B. Anderson deMenocal

Investigating past ocean carbonate chemistry. Atmospheric temperature has been closely associated with carbon dioxide concentrations during the past 800,000 years, as revealed by Antarctic ice cores, but many questions remain regarding the specific links between greenhouse gases and Earth's climate. From a marine geochemical perspective, I aim to clarify the ocean's role in past global carbon cycling and climate variability. First, I am developing and calibrating a new proxy for the ocean carbonate system: B/Ca of planktic foraminiferal calcite. In seawater, aqueous borate concentrations (B(OH)4

-) increase with pH. If borate is the dominant species incorporated into calcite (as boron isotopic evidence suggests), then B/Ca of carbonates should also increase with pH – indeed, this is largely what has been observed in organic and inorganic calcites. Together, these observations form the basis for the B/Ca-pH proxy. Before this proxy can be applied with confidence, however, specific controls on foraminiferal B/Ca need to be quantified and inconsistencies between existing B/Ca records need to be addressed. To this end, I have been growing live foraminifers under different seawater conditions (such as pH, carbonate ion, salinity, and temperature). The tightly controlled conditions in these culture experiments allow us to isolate variables whose

influences on shell chemistry are very difficult to discern in unconstrained, open-ocean sediment studies. I am also investigating micro-scale features within single shells using laser-ablation mass spectrometry to gain further insight into B incorporation and biologic controls on calcification. Second, I am testing the relevance of culture results to the open ocean environment by comparing my calibrations with natural samples taken from recently deposited sediments in the Gulf of Mexico. Finally, I will apply these validated calibrations to marine sediments to illuminate the relationship between ocean chemistry and global climate. I hope to generate high-resolution records of surface-ocean carbonate chemistry with multiple proxies to quantify upwelling of high-CO2 waters at key locations in the past. Depending on the sensitivity of B/Ca to the carbonate system, we may also investigate the influence of atmospheric CO2 on Northern hemisphere glaciation and glacial-interglacial transitions throughout the Quaternary.

PETER ALMASI 3/03 deMenocal Cane

North Atlantic Holocene Paleoceanography and Millennial Climate Cycles. North Atlantic climate has varied on centennial to millennial time scales throughout the Holocene. To assess the magnitude and spatial pattern of sea surface temperature (SST) changes during the Holocene, the feasibility of paired planktonic d18O and Mg/Ca is assessed. Reconstructions are generated for three sub-polar sediment cores at 40-60 year time resolution from 0-14000 BP. I. Assessing paired d18O and Mg/Ca in the Holocene North Atlantic The potential of paired Mg/Ca and d18O measurements to resolve 1-2 °C SST variability in the Holocene North Atlantic was evaluated in G. bulloides and N. pachyderma (d.) foraminifera. Individual components of external (calibration) and internal (measurement) errors were derived from existing calibrations, core tops from this study, and tests of cleaning procedures and laboratory reproducibility. To test the sensitivity of Mg/Ca in G. bulloides and N. pachyderma (d.) across a sub-polar North Atlantic SST gradient, paired Mg/Ca and d18O were

measured in 7 core top samples containing post-1950 radiocarbon. An exponential curve fit to Mg/Ca vs. d18O-derived calcification temperature yielded the relation Mg/Ca=0.851±0.052*e^(0.074±0.006*T). Mg/Ca from N. pachyderma (d.) does not appear sensitive to calcification temperature in these samples, an unexpected result that may reflect sample dissolution during intense cleaning procedures. II. Holocene climate from d18O and Mg/Ca in G. bulloides down-core records Surface water proxy reconstructions of temperature and salinity can provide insight into mechanisms of centennial-millennial Holocene climate change by the magnitude and spatial pattern of their variability. Foraminiferal d18O and Mg/Ca from cores in the central and eastern North Atlantic suggest that temperature and salinity varied up to 3°C during centennial to millennial cycles throughout the Holocene. Modern gradients in foraminiferal d18O and Mg/Ca were maintained between coring sites on the Björn Drift (Reykjanes Ridge) and Feni Drift (eastern Rockall Plateau) within sample replicate error throughout the Holocene. This suggests climate change in the spatial pattern representing southward movement of the sub-polar front during centennial to millennial scale cooling. Shifts in millennial-scale reconstructed d18O and Mg/Ca are more consistent between the central and eastern North Atlantic cores than with petrologic tracer indicators of drift ice or cosmogenic proxies for solar variability. No reply; no change since 7/08.

RAFAEL ALMEIDA 4/09 Christie-Blick Anders Hemming

I am looking at patterns of crustal extension in Southern Nevada. By re-evaluating the constraints on amounts of extension in the Lake Mead Domain of the Basin and Range, I will try and determine the validity of the proposed mechanisms for crustal extension in the region. Given that this region has been pivotal for the development of ideas regarding crustal extension, this re-evaluation is important for extensional processes in general.

No change since 7/09.

JENNIFER AMINZADE 4/08 Rind Del Genio Rosenzweig deMenocal

Future Water Availability in a Warming World As climate warms during the 21st century, resultant changes in water availability are an extremely important issue for society, perhaps even more important than the magnitude of warming itself. Yet our climate models disagree in their forecasts, limiting our ability to plan accordingly. This disagreement must be examined more closely to determine its causes. Therefore, I plan to improve our understanding of potential future water availability changes in seven water-sensitive regions by: 1) Assessing the forecasts of future water availability changes for these regions from five different models, using different metrics of water availability 2) Comparing the atmospheric dynamical processes that produce rainfall and drought in the real world to the way it occurs in five different climate models for these regions 3) Determining how these processes change as climate is forecast to warm during this century in the model simulations 4) Using these results, identify model strengths and weaknesses in making future water predictions From the above effort I hope to be able to suggest which Atmosphere-Ocean General Circulation Models produce the most realistic forecasts of future water availability, and identify what processes need improvement before any forecast can be made with confidence. This will dovetail with work I have already completed comparing the different metrics of future water availability change. No change since 7/08.

JENNIFER ARBUSZEWSKI 4/08 deMenocal B. Anderson Cane

A Global Multi-species Mg/Ca Calibration

The use of planktonic foraminiferal Mg/Ca ratios has become a popular proxy for reconstructing past sea surface temperatures (SST). One of the great appeals of this proxy is that it can be combined with shell δ18O values (which are obtained from the same material) in order to reconstruct

changes in the local δ18Oseawater, a proxy for ocean salinity. Inorganic calcite precipitation experiments indicate an exponential relationship of calcite Mg/Ca ratio with temperature. The exponential relationship with temperature holds true for foraminiferal systems, although there are significant vital effects. Published foraminiferal calibration studies indicate that temperature is the primary control on the shell Mg/Ca values. However, we have recently discovered what appears to be a salinity effect on the Mg/Ca signal recorded in planktonic foraminifera. This effect has been noted in several other recent studies as well (in the Mediterranean by Ferguson et al., 2008 and globally by Mathien-Blard and Bassinot, 2010). This effect causes excess Mg to be taken up by planktonic forams in high salinity regions. We have developed a new set of calibration equations for the Atlantic Ocean (and globally) using paired Mg/Ca and δ18O measurements, along with the bottom water ΔCO32-, to predict for temperature and salinity. Our results for G. ruber (white), which are validated using published coretop values, indicate that these equations are robust. My thesis work aims to extend this study globally with the goal of determining global equations for temperature and salinity for this species of planktonic foraminifera (G. ruber (white) and G. sacculifer) using coretop samples and validating those results with published coretop data. These new equations will be applied to downcore records from sites in the Mediterranean Sea and the Atlantic, Pacific, and Indian Oceans to test the validity of our new equations as they apply to reconstructing past oceanographic conditions. In order to better understand the nature of the excess Mg and the mechanisms by which it is incorporated into the shell, I have carried out additional experiments. SEM and flow through ICP-MS results indicate that the chemical cleaning is thorough and the excess Mg is not due to overgrowths or contamination. Shell morphology is consistent across the full range of salinities, alkalinities, and excess Mg (for G. ruber (white)). In light of these results, the excess shell Mg appears to reside within the primary structure of the calcite lattice. To further investigate the distribution the excess Mg/Ca within the shell structure, we use elemental maps generated by an electron microprobe. Although not definitive, these maps show significant heterogeneities of shell Mg/Ca that have correlations with the salinity environment in which the shell grew. These results will be widely applicable to

paleoceanographic studies and should allow more accurate reconstructions of both temperature and salinity in the past.

AMY BALANOFF 4/07 Norell Flynn Olsen

Phylogeny and Endocranial Evolution of Oviraptorosaur Theropods Oviraptorosaurs are an unusual group of theropod dinosaurs who possess an array of avian-like features. These morphological similarities have been used in some phylogenetic analyses to propose a close relationship between the two groups. Other analyses, however, suggest that this clade, along with therizinosaurs, is most closely related to Paraves (Deinonychosauria + Avialae). In order to understand the placement of oviraptorosaurs within Theropoda the relationships within this clade need to be resolved. I, therefore, propose to perform a phylogenetic analysis of the relationships within Oviraptorosauria to help place this important group within a larger evolutionary context. I will then use these relationships to elucidate the acquisition of neuroanatomical features that appear to be shared between oviraptorosaurs and birds.

STEPHEN BRUSATTE 5/10 Norell Flynn Olsen

Phylogenetic relationships of basal coelurosaurian theropods and macroevolutionary patterns in Mesozoic theropod dinosaurs.

ANTONIO BUONO 5/08 Walker Ebel Kelemen

An experimental study of the formation and evolution of planetary cores. We are using high-pressure/high-temperature techniques to study partitioning between the inner and outer cores of small planets, as well as the phase equilibrium that may govern the composition of those cores. No change since 7/08.

WEI DU 5/08 Walker Kelemen Harlow

Grossular-pyrope Garnet Series Solution Properties Garnet on the join Mg3Al2Si3O12 – Ca3Al2Si3O12 (pyrope-grossular) is considered to be one of the most important solid solutions in the Earth’s crust and upper mantle. Agreement between the different models of garnet mixing properties based on former experimental data is not very satisfactory. So in my thesis, I will present the unit cell parameters of garnet solid solutions on the pyrope-grossular join synthesized at Lamont-Doherty Earth Observatory (LDEO) using multi-anvil technique and measured by X-ray diffraction at Lawrence-Berkeley National Laboratory. I measured the volume changes in this garnet solid solution between 25 and ~600°C and calculated the excess volume and thermal expansion in this temperature region. By fitting my new data to a thermal dynamic model, the new coexisting PT region for two phases garnet with composition on this pyrope-grossular join will be found and we will also hope to know how the consolute temperature changes with pressure. Then I will compare the modeling result with the following phase separation experiment result. And also I will check some natural garnets to see how their growing PT conditions will change concerning my new data and the revised thermal dynamic model.

No change since 7/08.

ELI DUEKER 3/09 Uriarte Griffin Juhl Connecting Water Quality with Air Quality through Coastal Microbial Aerosols Although the transfer of marine microbes from surface waters to aerosols through bubble release has long been recognized, the microbial aerosol emissions from surface waters at the coastal interface have yet to be constrained. I will combine microbiological, oceanographic and atmospheric approaches to contribute to a better understanding of this connection between air quality and water quality both in the natural coastal environment and in the urban setting.

ANNA FOSTER 4/10 Ekstrom Nettles Gaherty Surface wave propagation and the velocity structure of the western US The composition and structure of the interior of the earth are inaccessible to physical observation, and instead must be investigated remotely. My research approaches this using teleseismic surface waves that have been recorded on the USArray Transportable Array. Using a new two-station method, the inter-station phase is measured and inverted for a phase velocity model at discrete periods. My thesis work will continue to investigate the complicating effects of wave propagation and ways to improve the model, as well as to solve for a three-dimensional model of the crust and upper mantle velocity structure in the western United States.

ALISON HARTMAN 4/10 Goldstein B. Anderson Hemming

Neodymium Isotopes in the Atlantic Ocean Neodymium (Nd) isotopes are an important water mass tracer in the Atlantic ocean. Records of the bottom water Nd isotopic composition have been preserved in an array of substrates within deep sea sediment cores and can be used to investigate how the Nd signal has changed throughout time. We compare the record derived from varying substrates in order to define the accurate Nd signal. By determining the Nd signal in interesting regions of water mass mixing, we can investigate paleoceanographic questions. For this project, we seek to determine changes in the deep water Nd composition in the South Atlantic. This region is the most southern extent of North Atlantic Deep water, which is often used to monitor changes in meridional overturning circulation during glacial to interglacial transitions. Nd isotopes measured from modern day seawater samples in the North Atlantic can be interpreted in ways other than water mass mixing. Dust, hydrothermal vents and boundary exchange are potential sources of Nd to the ocean. We will seek to understand how these inputs affect the isotope composition. Can local inputs in the North Atlantic explain variations in the paleoceanographic records of the South Atlantic or do we see changing mixing components as a result of global climate shifts and oceanographic reorganization?

JANELLE HOMBURG 6/09 Kelemen Spiegelman Holtzman Strain Localization in Viscoelastic Materials Viscoelastic strain localization is frequently observed in nature. However, while there are a number of material properties (e.g. melt fraction, water content, grain size) that are known to affect the rheologic behavior of viscoelastic materials, how those effects interact to promote or inhibit strain localization is unknown. In order to investigate the process of strain localization I utilize both natural samples from the Oman, Josephine and Trinity Ophiolites and numerical models that investigate the effects of variations in initial grain size distribution and rate of grain growth/reduction. In addition my results are also used to investigate the effectiveness of the extrapolation of experimentally determined flow laws from experimental conditions to geologically relevant conditions. No change since 7/09.

TIANXIA JIA 4/09 Lerner-Lam Kim Martinson

Advanced analysis of complex seismic waveforms to characterize subsurface structure. my research focus on using advanced statistical and signal processing techniques to analyze complex seismic waveforms. The aim is to better understand the earth structure in both large and regional scale. My first project is body wave analysis of the subduction structure under the Tyrrhenian Sea, Italy. I use dispersion analysis, frequency-domain scattering and attenuation analysis to study the complicated Calabria subduction system. I am also interested in using cross-correlation technique to investigate subsurface structure, particularly for the urban area seismic hazards study. The data I use is ambient noise, or microtremor measurements data obtained from portable array. This involves advanced statistical analysis of time series data, and inversion for seismic velocity structure, etc. I've done field work in Manhattan and Charleston, South Carolina to collect data. I am currently working on developing some cutting-edge global optimization techniques to solve complicated geophysical inverse problems, methods include Monte Carlo, simulated annealing, etc.

JASON JWEDA 6/09 Goldstein Kelemen Plank

Constraining source contributions to arc lavas using isotopic and trace element fingerprints

A long-standing debate in arc magma genesis

research has been whether or not contributions from the downgoing slab can be distinguished from crustal processes for lavas of arc volcanoes situated above thick continental crust. The Quaternary Tatara-San Pedro complex (TSPC) in the southern volcanic zone (36°S) of Chile is an ideal location to discern subduction component contributions as it is a long-lived volcanic center (~930 ky of activity) that overlies the thick (30 – 35 km) Chilean continental crust. In this study, I am measuring radiogenic isotopic tracers including 87Sr/86Sr, 143Nd/144Nd, 176Hf/177Hf, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb on a suite of mafic volcanic rocks that represent two of the eruptive sequences at the TSPC. Together with trace elements, isotopic ratios will be utilized to constrain the source and contribution of subducted slab-derived components to the TSPC.

No change since 7/09.

JENNIFER LEVY 4/09 Griffin Schuster Peteet

The belowground carbon cycle at Black Rock forest I am interested in characterizing the belowground carbon cycle and understanding the mechanistic controls of carbon movement through this system. My work is focused on quantifying the total belowground carbon and its distribution among the several carbon pools, understanding the influence of species dominance on the partitioning of autotrophic and heterotrophic sources to soil respiration, and characterizing the relationship between the seasonal cycle of soil respiration and environment. No reply; no change since 7/09.

JING LI 12/08 Lacis Del Genio Ou

Atmospheric aerosols play very important roles in anthropogenic forcing of climate change. They have the direct effect by scattering sunlight back to space, as well as the indirect effect by interacting with clouds. Moreover,

absorbing aerosols also have the semi-direct effect of suppressing convection and reducing cloud formation by heating the atmosphere. Aerosol composition, i.e., fraction of absorbing/non-absorbing aerosols, which is reflected in aerosol Single Scattering Albedo (SSA), is essential in determining their radiative effects. However, currently this piece of information is largely uncertain. My research involves investigating the temporal and spatial variation of absorbing aerosols using satellite and ground measurements and the GISS GCM. I also estimate the dependence of aerosol radiative forcing on SSA through model simulations. The Absorbing Aerosol Index (AAI) product from Total Ozone Monitoring Spectrometer is the only long-term record of absorbing aerosols. The first part of my thesis focuses on the analysis of the AAI data. I also evaluate the GISS GCM absorbing aerosols field by constructing an AAI simulator with the model and directly compare with satellite measurements. AERONET is a net work of ground measurements of aerosol properties and also provides retrievals of SSA. In the second part of the thesis, I will analyze the long term trends of SSA as well as other aerosol properties from selected stations. I will also validate and improve GCM simulations based on AERONET data. Moreover, aerosol composition information also affects satellite retrievals of aerosol properties, because the SSA value of different aerosol models must be assumed a priori. The third part of my thesis involves assessing satellite retrievals from Moderate Resolution Imaging Spectroradiometer (MODIS) using AERONET measurements and investigating possible influences of SSA assumptions. And finally, I will conduct a series of sensitivity studies using the GISS GCM to evaluate the influence of SSA on the estimated radiative forcing of aerosols.

XINFENG LIANG 4/10 Thurnherr Gordon Takahashi

Investigating the Dynamics of Ridge-Crest Currents using Observations and Process Models Description: The physical oceanography in the vicinity of mid-ocean ridges is important in a variety of different

contexts, including the global overturning circulation and the biogeography of chemosynthetic organisms endemic to hydrothermal vent fields. However, in many parts of the global ocean, very little is known about the deep currents near mid-ocean ridges. In the context of the NSF-funded LADDER project, aimed at investigating the dispersal of larvæ of hydrothermal organisms on the crest of the East Pacific Rise near 10N, a large physical oceanographic data set was collected, and a regional circulation model was constructed. Both observations and numerical results indicate that the sub-inertial circulation near the ridge crest is dominated by a pair of anti-cyclonically sheared boundary currents associated with velocities of several cm/s. The observations and model predictions are remarkably similar to observations from the Juan de Fuca Ridge near 45N. These observations from two very different regions in the deep ocean suggest that ridge-crest boundary currents may be common and, therefore, important for horizontal mixing and dispersal near mid-ocean ridges. In order to gain an understanding of the dynamics of ridge-crest boundary currents, I propose to use an integrated approach consisting of data analysis and numerical process experiments. The primary goals of my thesis work include 1) evaluation of the relative contributions of the different terms in the governing equations, 2) determination of the sensitivity of the ridge-crest boundary currents to different environmental parameters and different forcing properties, and 3) an investigation into the nature of the sub-inertial “background” variability that gives rise to the ridge-crest boundary currents. In addition to the primary goals, some other physical processes, such as internal tides, near-inertial waves and ocean mixing could also be investigated.

MILENA MARJANOVIC 4/09 Carbotte Webb Mutter

My research is concentrated on mid-ocean ridges, the Juan de Fuca Ridge and East Pacific Rise. I am investigating crustal structure formed at these spreading centers and its evolution using multi channel seismic data and gravity data. In particular I am interested in ridge segmentation processes (investigating sources present in the lithosphere and their bathymetric expressions). I am also interested in ridge hot-spot interaction that has prominent effect on formation of

the crust and is possible linked to processes leading to ridge propagation.

ABBY MAULDIN 3/05 Schlosser Smethie Martinson

Transient tracer studies of ocean circulation in the Arctic Ocean andNordic Seas I) Deep water formation and exchange rates in the Greenland and Norwegian Seas in the 1990s: Inferences from box model calculations using tritium-helium and CFC's The deep waters of the Greenland and Norwegian Seas have become warmer and saltier as a result of a reduction in the formation rate of Greenland Sea Deep Water after 1980. A box model of deep water formation and exchange, based on two decades of transient tracer measurements, is used to calculate the ventilation rates in the deep waters of the Nordic Seas and the Eurasian Basin of the Arctic Ocean. II) Estimating the velocity and mixing timescale of the Arctic Ocean Boundary Current with transient tracers The Arctic Ocean Boundary Current is a persistent, large-scale feature that transports water of Atlantic origin around the Canadian and Eurasian Basins. The boundary current is modeled as a leaky pipe and tritium-helium data are used to calculate the mean velocity of the boundary current and the mixing timescale between the boundary and the interior. III) Sources of freshwater in the East Greenland Current, 2002, from water mass analysis using oxygen isotope data The East Greenland Current transports freshwater from the Arctic Ocean via the climatically sensitive Nordic Seas to the subpolar North Atlantic. Assessing the leakage of freshwater from the EGC into the Nordic Seas is important because freshening in the surface of the Greenland and Iceland Seas inhibits convection and the renewal of dense intermediate and deep waters. A thorough understanding of the Arctic freshwater budget is also a prerequisite for predicting the future of Arctic sea ice. Here, the components of freshwater in the East Greenland Current are analyzed using a weighted, least-squares method that incorporates oxygen isotopes, salinity, nutrient and alkalinity data from 2002. The relative contributions of meteoric water, sea ice melt and Pacific water are quantified

and contextualized within the freshwater budget of the Arctic. No reply; no change since 7/09.

IVAN MIHAJLOV 4/10 Stute Schlosser vanGeen Zheng

Protecting the low-arsenic, deeper aquifers of Bangladesh: a detailed study of arsenic sorption and transport in a complex geohydrologic setting Deeper, often Pleistocene-age, aquifers in Bangladesh are currently one of the major mitigation options for the widespread arsenic poisoning in the country caused by drinking contaminated shallow groundwater. However, this resource is threatened by increasing exploitation, which can lower the pressure at depth and induce a downward flow of high-arsenic shallow groundwater. The goal of my research is to study how the potential plume of arsenic would move through the deeper aquifer. The question is approached from both the chemical and physical aspects of arsenic (and water) migration. I study the sorption of arsenic onto aquifer’s sediments by batch, column, and field experiments. The extent, reversibility and rapidity of sorption are important factors in slowing down the transport of arsenic. In parallel, my study also aims to answer local hydrologic questions about the aquifers through studies with pumping tests and groundwater tracers such as bromide, 14C, 3H, or stable isotopes. Specifically, of interest is the amount of dispersion in the deeper aquifer, its degree of hydraulic connectivity with the contaminated zones, the current residence time of the groundwater, and whether there are signs of younger, shallow groundwater intrusion.

KORI NEWMAN 4/06 Menke Cormier Nedimovic My research spans on two distinct areas. The first is a geophysical and geochemical survey of seafloor seeps and the second is tomographic modeling of the upper crust at mid-ocean ridges. My first chapter is an investigation of giant seafloor pockmarks (average dimensions are 2 km long x 1 km wide x 50 m deep). Previously collected chirp seismic images revealed subsurface gas beneath the features, so we returned to the site to collect data to determine if any active venting is

occurring. Our survey included two emerging technologies, an Autonomous Underwater Vehicle (AUV) which collected data while flying ~3 m above the seafloor and a METS methane sensor which was mounted on the AUV and collected underway dissolved methane concentration measurements, in addition to more traditional methods including coring and hydrocast water sampling were. Successful interpretation of our data involved determining the response function of the METS sensor and devising an algorithm to correct for it. The synthesis of the data confirmed that methane is being released through the seafloor and allowed us to map the general spatial distribution of vent sites. For my second chapter, I computed travel time tomography models using the refracted rays recorded during a multi-channel seismic (MCS) survey at the Juan de Fuca Ridge. MCS data are usually used to produce images of the subsurface using the reflected rays, but at the farther offsets, refracted rays arrive before the seafloor reflection and can be used to compute tomographic models using first arrival techniques. The data I used are from long, axis-perpendicular transects across three segments of the ridge system. The resulting models are the highest known resolution velocity models of seismic layer 2B and yield information about the evolution of layer 2B as well as how other geologic processes alter layer 2B velocities. My third chapter involves streamer tomography as well, this time collected along the fast spreading East Pacific Rise. For this project, the data are first downward continued to simulate placing the seismic sources and receivers closer to the seafloor. This allows the refractions from seismic layer 2A to be picked in addition to layer 2B, resulting in an inversion that simultaneously solves for the velocity structure of both layers. No change since 7/09.

ELIZABETH PIERCE 4/10 Hemming T. Williams Broecker

Antarctica's Geologic and Climatic History from Isotopic Sedimentary Provenance Studies of Marine Sediments My research applies geochronology and radiogenic isotopes in minerals and bulk sediments to constrain the subglacial geology of Antarctica and to apply this geological information to tagging paleo-iceberg discharges from the

Antarctic Ice Sheet. My primary approach is to apply the 40Ar/39Ar age of detrital hornblende grains. Hornblende is a relatively abundant, rock-forming mineral, that records the last major tectono-thermal event in a region. It has been previously demonstrated that hornblende ages provide a robust division of Antarctica that conforms to the natural glacial divides around the continent. My work is a combination of more precise documentation of the geological history, and the application of the approach to the paleo-climate related changes in the Antarctic Ice sheet. My first chapter is a spatial survey of 40Ar/39Ar age populations of detrital hornblendes and biotites in conjunction with neodymium isotopes. My samples are from piston cores, the locations of which span the East Antarctic coastline from the Ross Sea west to Prydz Bay,as well as from intervals from ODP1165 that are rich in ice rafted detritus. It is important to establish the boundaries of geologic terranes along this margin if we want to do sedimentary provenance studies; given that 98% of East Antarctic is covered in ice averaging ~3 km thick, looking at glacially derived marine sediments enables us to characterize the geology that is obscured by the ice sheet. Along this margin there is much variation in the 40Ar/39Ar hornblende ages, due to East Antarctica's complex geologic history. Much of East Antarctica is characterized by Pan-African (~500 Ma) and Ross Orogen (~400-500 Ma) overprinting, with the exception of the Wilkes Land (~1100-1300 Ma) and Adélie Land (>1500 Ma) margins. My results provide strong evidence that the Wilkes and Adélie margins produced massive armadas of icebergs several times in the Miocene and the Pliocene. My second chapter is a comparison of detrital 40Ar/39Ar hornblende and U-Pb zircon age populations from marine sediment cores around East Antarctica. U-Pb ages of detrital zircon grains have provided an extrordinary tool for sedimentary provenance work, given that they are ubiquitous, resistant to damage and weathering, and that the U-Pb age records the crystallization age of the mineral. Although not as widely used, 40Ar/39Ar dating of detrital hornblende grains can also serve as a powerful sedimentary provenance tool, particularly in situations where chemical weathering is minor. Certain natural biases exist between these two mineral chronometers. Zircon is an accessory mineral that is common to a wide variety of rocks, but occurs in particularly high concentrations in felsic crystalline rocks. Hornblende is a rock-forming mineral, and it is particularly abundant in intermediate and mafic

crystalline rocks and in amphibolites. In contrast to the resistance to resetting and destruction that characterizes zircon, hornblende is relatively susceptible to weathering and thus is not typically found in recycled sediments. Additionally, the 40Ar/39Ar system in hornblendes has a closure temperature (~500˚C). Thus, for areas which have experienced a polymetamorphic history, e.g, East Antarctica, combining the two approaches can provide added detail to provenance studies. My third chapter will be a detailed examination of IRD peaks spanning the mid-Miocene transition. The sample are from an IODP core from off of the Wilkes Land Margin as well as from ODP1165 in the same interval. The interval of interest spans the mid-Miocene transition, a second major step in the growth of the East Antarctic ice-sheet, following its inception ~34 Ma. This study will involve grain size analysis, and the geochemical measurements (e.g. 40Ar/39Ar dating of hornblende and biotites, U-Pb dating of zircons and neodymium isotopes).

KANDAGA PUJIANA 3/08 Gordon Ou Martinson

The Makassar Strait dynamics at intra-seasonal time-scales. My research focuses on the characteristics of Indonesian Throughflow [ITF], water mass and heat transport from the Pacific to Indian Ocean, at intra-seasonal [20-90 days] timescales observed in the main conduit of ITF, Makassar Strait. The local atmospheric perturbation play a substantial role in forcing intra-seasonal variability [ISV] within the mix layer of Makassar Strait, and two remote oscillations from the Indian Ocean and Sulawesi Sea [western most basin of the Pacific Ocean] contribute significantly to the rich texture of ISV over the thermocline and deep layer of Makassar Strait. The remotely forced ISV emanating from the Indian Ocean propagates along the waveguide through Lombok Strait in a waveform resembling a hybrid baroclinic topographic-Kelvin wave, while the internal eddies moving with a speed of a baroclinic Rossby wave into Makassar Strait are remotely generated in Sulawesi Sea. The dynamics of the remotely forced baroclinic topographic-Kelvin wave and internal eddies that disperse their energy into Makassar Strait are investigated within the context of wave-number analysis, energetics or energy flux, wave-topographic interaction, wave-mean flow interaction, and the influence of ENSO and IOD. In situ and remotely

sensed oceanographic-atmospheric datasets, analytical and numerical modeling approaches are utilized in the analysis.

No change since 7/09.

DANIEL RUIZ 7/09 Thomson Cane Martinson

My research activities aim to contribute to the adaptation strategy to climate change in Colombia. Analyses are focused on two different areas of interest: Andean high mountain ecosystems (paramo ecosystems) and infectious diseases (vector-borne diseases). My research on paramo ecosystems proposes a six-tiered approach to understand the linkages between the ongoing changes in climatic conditions and the disruptions affecting the integrity of high-altitude environments. Activities include: analyses of changes in atmospheric stability and lifting condensation levels; diagnosis of changes in hydrological regimes; assessment of the extent of life zones; analyses of increases in the spread of high mountain fires; assessments of the integrity of paramo ecosystems; and analyses of increases in climatic stress. My research on vector-borne diseases is focused on a highly complex multi-factorial disease: malaria. I am using malaria process-based models to offer useful information that could effectively guide decision-makers in risk assessment, malaria control investments and choice of interventions. I am using the dynamical models to: estimate the timing and possible magnitude of unexpected malaria outbreaks; explore the role that both climatic and non-climatic factors play in fluctuations and trends in malaria incidence; analyze key confounders; investigate current decision making processes; provide quantitative goals for effective interventions; pose and answer 'what if' questions; and, finally, help decision makers learn. No change since 7/09.

SONALI SHUKLA 4/09 Chandler Sohl Del Genio Rind

Atmospheric Circulation of the Indian Ocean Region in a Warmer Climate: The Impact of Altered Sea Surface Temperatures The first chapters of my thesis investigated the contribution of altered Pacific and Indian Ocean sea surface temperatures (SSTs) to the atmospheric circulation and

teleconnections during the warm Pliocene period. This work indicated that amplified high latitude warming, in conjunction with altered Pacific and Indian Ocean SST gradients, can alter the mean moisture transport and atmospheric of the Indian Ocean region, specifically around East Africa, India and Indonesia. In fact, the response of the greater Indian Ocean atmospheric circulation to globally warmer conditions is still largely uncertain. In particular, it is necessary to bracket changes in the South Asian Summer Monsoon (SASM), which is responsible for over 75% of the annual regional rainfall, as underlying and remote SSTs begin to warm or exhibit altered patterns with climate change. My thesis will characterize potential changes to the SASM due to altered Indo-Pacific SSTs resulting from climate change, outside of the observed interannual variability. To do this, I am employing the use of the Goddard Institute for Space Studies general circulation models run with various paleoclimatic and future-projected global warming scenarios in which tropical SSTs exhibit permanent changes. The characteristic features of the SASM, its general circulation, energy balances and moisture transport will be evaluated under these warm climate scenarios. The end result of the work is to determine what GCM-produced quantities (i.e. zonal winds, precipitation) would be most useful in determining changes to the SASM under projected climate changes. The relevance of this work is underscored largely by the demand from Indian Ocean agrarian societies, which rely heavily on the SASM rainfall, to anticipate how crop production and food security may change in the next several decades. By using a warm-climate scenarios based approach, we can analyze possible limits to SASM circulation changes, as well as the warm-climate implications for the regions rainfall. The last stages of my thesis will be to evaluate how well the GISS GCM reproduces the observed SASM characteristic features, as well as summarize where the GISS model falls in the span of all GCMs in simulating this phenomenon. To this end, I will also evaluate how the model’s SASM reacts to current changes in SSTs associated with major climatic oscillations such as ENSO and the more recently discovered Indian Ocean Dipole (IOD). Upon the completion of this work phase, I will next look at the impact of future-projected warm climate scenarios, as specified by the IPCC Special Report on Emissions Scenarios, on the SASM circulation. I will compare these results with the Pliocene period simulations previously performed. I will also be able to compare transient Indian Ocean regional response with equilibrated

warm-climate runs to establish if there is a tendency in the SASM reaction to (increasingly) warmer conditions.

ASHLEY SHULER 4/09 Ekstrom Gaherty Menke

Investigations of Anomalous Earthquakes Associated with Active Volcanoes Recent advances in earthquake detection and location have revealed a class of previously undetected, moderately sized, slow earthquakes occurring near active volcanoes. Many of these earthquakes are highly non-double couple in nature, and have moment tensors that are suggestive of slip on ring fault structures (vertical-CLVD). As several of these earthquakes are temporally associated with dome or crater collapses, paroxysmal explosions and other types of eruptive activity, it is likely that these earthquakes are characteristic of changes internal to magmatic plumbing systems. In my thesis work, I characterize these earthquakes and explore the relationship between their occurrence and large-scale magma movement. 1. Systematic global search for vertical-CLVD earthquakes associated with active volcanoes, studying events with both normal and long source durations. I model these earthquakes and relate them to local geologic and geophysical observables to determine if this class of earthquakes is characteristic of a particular type of magmatic activity or type of volcano. 2. Analysis of a subset of five vertical-CLVD earthquakes associated with Nyiragongo Volcano and investigation of their source mechanism. I attribute these events to the collapse of shallow magma chambers triggered by diking events. 3. Study of the seismicity associated with the two largest caldera collapses of basaltic volcanoes in the last century – Fernandina Volcano in 1968 and Miyakejima Volcano in 2000. I model the largest earthquakes of these sequences and constrain the progression of incremental collapse. 4. Modeling of stress changes associated with shallow magma chamber collapse. I examine how inflation and deflation of magma reservoirs can lead to slip on pre-existing ring fault structures.

No change since 7/09.

ADRIENNE SMITH 3/08 Bell Buck Lerner-Lam

Recent observation has shown the subglacial water can penetrate to the ice sheet bed and influence the velocity of an ice sheet on a relatively short time scale. Questions that this raises and my work aims to answer are 1.) Can we image the subglacial hydrological system? 2.) How is water transported beneath an ice sheet, in channels or broader flows? and 3.) What impact do subglacial processes have on the long term stability of an ice sheet? No reply; no change since 7/08.

MICHELLE SPAULDING 4/08 Flynn Norell Christie-Blick

Phylogeny of the stem Carnivoramorpha The living order Carnivora is one of the most diverse extant mammalian order. The fossil record of this order extends, undoubtedly, back to the early Paleocene, roughly 63 million years ago. However, it is not until roughly 42 million years ago that clear representatives of the crown group arise. The fossils found in the interim time (stem carnivormorphans') have typically received little detailed study, and many previous treatments of the order tended to lump them into untested groupings, or ignore them completely. My research is focused upon these basal specimens, in order to create a clear picture of the series of evolutionary transformations that led to crown Carnivora. Questions that will be addressed, primarily, are the phylogeny of the basal taxa - is there a clear stem line series of taxa or several clades within the stem? and locomotor behavior of primitive taxa, hoping to shed some light on the primitive locomotor method of the Carnivoramorpha. No change since 7/08.

SANPISA SRITRAIRAT 3/07 Peteet Griffin deMenocal Kenna

Multiproxies analyses of past vegetation, climate, and sediment dynamics in Hudson River wetlands. Hudson River Estuary is an important resource for millions of people. With anthropogenic changes and projected climate change, the ecosystem along the estuary can be

adversely affected. The objective of my research is identify past environmental changes along the estuary to understand how human and climate have changed the ecosystem. I have studied marsh sediment using pollen and macrofossils analyses to identify past vegetation, climatic shifts (including the Medieval Warm Period and Little Ice Age), and land use changes over the past 1000 years at two nothern Hudson River National Estuarine Research reserve sites, Tivoli Bays and Stockport Flats. We hope to undrestand the regional picture of the changes in the estuary. Thus, we are devevloping a more rapid way to analyze sediment cores for land-use and climatic changes using X-Ray Fluorescence analysis of sediment elemental composition. I will analyze sediment cores from over 15 sites as a N-S transect along the estuary in order to understand this regional changes. No change since 7/09.

LISA STREIT 4/10 Kelemen Matter Spiegelman

Carbonation of peridotite in the Oman Ophiolite When exposed to water and CO2 at earth's surface, tectonically mantle peridotite reacts rapidly to form solid carbonate minerals, such as magnesite, dolomite, and calcite, as well as secondary silicate minerals like serpentine, quartz, or talc. In the Oman Ophiolite, these reactions are manifested (1) in active, on-going low-temperature systems involving meteoric water, which result in serpentinization, carbonate vein formation, and travertine precipitation at alkaline springs, and (2) in older, higher-temperature systems, which resulted in completely carbonated peridotite, known as listwanite. These natural processes of hydrothermal alteration and weathering could potentially be accelerated to provide a permanent storage solution for the disposal of CO2 via the in situ formation of solid carbonate minerals in peridotite. My research focuses on constraining the conditions under which natural carbonation has occurred in the Oman ophiolite, with the goal of understanding what factors and feedbacks control efficient carbonation of peridotite. This work includes field studies, petrologic observations, geochemical modeling, stable isotope thermometry, and reaction rate models.

DANIELLE SUMY 3/08 Tolstoy Gaherty Menke

Exploring the Mechanisms of Earthquake Activity at Extensional Plate Boundaries: Studies from 9º50’N East Pacific Rise and the Gulf of California

Like the seams of a baseball, the global mid-ocean ridge system encircles our globe, extending approximately 80,000 km in length and creating new oceanic crust at the rate of centimeters per year. Much of the volcanism along mid-ocean ridges is emitted during short periods of eruption, along cracks or fissures, and only after the build-up of stress along the plate boundary. Thus, the rare occurrence of volcanic activity and the deep burial of these systems beneath kilometers of water and sediment make the study of mid-ocean ridge volcanism and tectonism complicated. The study of seismic activity along these plate boundaries, however, can illuminate zones of cracking and fissuring where recent eruptions have occurred, identify regions of impending volcanism, and elucidate the location of strain build-up. Therefore, my dissertation focuses on seismicity recorded by ocean-bottom seismometers (OBSs) at the 9º50’N East Pacific Rise (EPR) hydrothermal vent site, an intensely studied, fast-spreading mid-ocean ridge (~110 mm/yr), and within the Gulf of California (GoC), where seafloor spreading is just beginning. The four chapters of my dissertation focus on the following problems: 1. Does seismic activity at the 9º50’N EPR occur preferentially with tides? 2. Are there spatial variations in tidal triggering within the 9º50’N EPR hydrothermal system? 3. Is strain localized on the plate boundary within the GoC? Are the mechanisms of on or off plate boundary activity different? 4. Are slow-slip events (precursors to large seismic events) occurring on the oceanic transforms within the GoC? No change since 7/09.

ZACH TESSLER 2/09 Gordon Thurnherr Martinson

Strength and variability of the Panay Sill Overflow and its role in the regional Philippine circulation.

The Panay Sill is the main source of water to the upper Sulu Sea, in the Philippine Archipelago. The overflow across the sill exhibits variability on tidal and seasonal timescales. This study will characterize this variability, as well as investigate potential longer-term variability, such as on ENSO-related interannual timescales, using both observational data and hydraulic control theory. Additionally, the configuration of the islands, straights, and basins in the Philippine Archipelago provides a setting to investigate processes acting on small spacial scales of less than 100 km. This research will attempt to better understand the mixing at Panay Sill and the role played by internal waves and hydraulic jumps in modifying the water that eventually makes up a significant portion of the Sulu Sea. No change since 7/09.

KAORI TSUKUI 4/10 Flynn Hemming Meng

High precision U-Pb and Ar-Ar geochronology of tuffs from the early to middle Eocene: implications for calibration of the Geomagnetic Polarity Time Scale and understanding the Bridgerian/Uintan land mammal turnover. The Geomagnetic Polarity Time Scale (GPTS) plays an integral role in interpreting geological records ranging from biological evolution, climate change to sea floor spreading, making the precision of its calibration a matter of fundamental importance to our understanding of Earth history. Currently, pre-Neogene part of the GPTS is calibrated via interpolation between a set of discrete calibration points, but according to this method, calibration of intervening magnetic chrons is highly sensitive to the number and accuracy of the tie points used. However, a more precise and stable timescale is needed in order to resolve geological and paleoclimatological records that are being recovered at an increasingly fine temporal resolution and also to correlate the record of mammalian faunal turnover between continents and against climatic data. To this end, I provide chronostratigraphic constraints on a series of tuffs from the Greater Green River Basin and surrounding basins in the Laramide foreland. These tuff beds are ideal as they have a potential to be used for U-Pb zircon and Ar-Ar

sanidine geochronology, paleomagnetic polarity determination and are often found interbedded with fossiliferous beds. A new calibration model that integrates all of the high precision radioisotopic, paleomagnetic polarity and paleontological data will enhance our ability to understand the dynamic interrelationships between the mammalian evolution as preserved in the Greater Green River Basin and the climate that reached the Cenozoic peak around this time.

JILL VanTONGEREN 4/08 Kelemen Mathez Goldstein

Thermal and Chemical Evolution of the Bushveld Upper Zone. The Bushveld Complex is the world's largest layered mafic intrusion and one of few layered intrusions with its roof still intact. My dissertation focuses on the thermal and chemical evolution of the uppermost portions of the Bushveld in order to understand the nature of heat loss and differentiation in large magma bodies. Specifically, my dissertation research aims to identify the magmatic inputs and outputs into the Bushveld Upper Zone magma chamber. Ultimately the conclusions of this research will have implications for the source and emplacement history of the Bushveld Complex and surrounding rocks.

DAVID WANG 3/05 Cane Khatiwala Chen

Tropical Pacific Ocean in a Warming Climate By analyzing a set of IPCC AR4 (CMIP3) climate models for the projection of the twenty-first century, it is found that the Pacific subtropical cells (STCs) show contrasting trends between two hemispheres in a warming climate. The STCs tend to be weakening (strengthening) in the northern (southern) hemisphere as a response to large-scale surface wind changes over the tropical Pacific. The pycnocline transport convergence into the equatorial Pacific Ocean from higher latitudes shows a robust weakening in the twenty-first century. This weakening is mainly through interior pathways consistent with the zonal flattening of the tropical pycnocline. In addition, there is a robust weakening of the Indonesian throughflow transport in a warming climate. The source regions and transit times of the Pacific equatorial thermocline waters in the present-day climate

and a warmer climate are investigated using simulated transit time distributions (TTDs) in an ocean general circulation model. The source regions of the equatorial thermocline waters are broad and comprise several major sources. It is found that the large-scale distribution of source waters and TTDs of the equatorial thermocline waters show little change in a warmer climate, except in the southern South Pacific where the contribution is somewhat larger and the transit times shorter in a warmer climate. The warming of the equatorial thermocline waters is almost entirely due to the warming of source waters rather than the changes in the location of source waters. The dynamic sea level changes in the tropical Pacific Ocean are investigated using a linear, wind-driven ocean models that embodies only equatorial wave dynamics. The linear, wind-driven solutions are compared against observed recent sea level trends by satellite altimetry and projected future sea level trends by IPCC AR4 models. It is found that both recent (1993-2008) and projected (2001-2100) tropical Pacific sea level changes can be well reproduced by the linear model. The effect of ocean stratification changes also plays a role in the future sea level trends in the tropical Pacific Ocean.

KAREN WOVKULICH 4/07 Chillrud Stute Mailloux Simpson

Mobilization of Arsenic from Contaminated Sediments My research focuses on arsenic cycling in the environment and specifically on the mobilization of arsenic from contaminated sediments at the Vineland Chemical Company Superfund site in southern New Jersey. Arsenic is the second most common contaminant of concern at U.S. Superfund sites, and contaminated groundwater is often remediated using pump and treat technology. However, arsenic can sorb to iron and aluminum oxyhydroxides in the sediments making pump and treat remediation less effective and thus slower to reach the desired level of clean up, as has been the case at Vineland. Therefore, my current research aims to improve the efficiency of pump and treat by increasing the mobilization of arsenic from the sediment into the groundwater that will then be treated. This research involves laboratory experiments in which I make chemical amendments to soil columns and monitor their effect on arsenic mobility as well as hydrological modeling and in situ

field testing of the most promising chemical amendments. The information gained from these laboratory and field studies should be applicable to numerous arsenic contaminated sites where pump and treat remediation is currently being used or where it may be used in the future. Additionally, what we learn from this work about factors that influence arsenic mobility may also help us understand arsenic cycling and mobilization in areas of the world where naturally occurring arsenic is contaminating groundwaters that are used for drinking water supplies. No change since 7/08.

WENCHANG YANG 4/09 Seager Cane Ting

The response of global monsoons to climate change Monsoons play an important role in the atmospheric circulation and the global hydrological cycle and influence lives of billions of people in the world. Therefore, it is both theoretically and practically crucial to understand how monsoons respond to climate change. We will first investigate monsoonal variability from 1979 to present to look at what has been happening to monsoons. The variability will be decomposed into natural component and the component that can not be explained by natural variability. The result will be compared to the IPCC AR4 model simulations during the same period, which can be used to evaluate the performance of models. After that, we will analyze model projections of the 21st century and use both simple and complex models to reveal the physical mechanisms behind these projections. Through this process, we hope to get a deep understanding on how monsoons will respond to climate change. No change since 7/09.

EMMI YONEKURA 4/10 T. Hall Camargo Del Genio

Typhoon Landfall in Different Climate States: a Statistical Track Modeling Study The western North Pacific is the most active ocean basin for tropical cyclone (or typhoon) activity, and many of these storms make landfall along heavily populated areas of the East Asian coast. With only about fifty years of reliable data, risk assessment of tropical cyclone landfall on small coastal regions, regions with few historical landfalls, or

landfalls during specific climate states becomes difficult. Therefore, I plan to construct and use a statistical track model to project data from the entire lifecycle of the historical tropical cyclones onto the coastlines. Climate oscillations, especially ENSO, have known effects on tropical cyclones. In constructing the track model, dependence on important climate states will be integrated using linear and Poisson regression techniques. Thus, the effects of ENSO, other climate variability influences, and anthropogenic climate change will be analyzed with respect to landfall. Further, the intensity of the tropical cyclones at landfall will be examined geographically and in relation to specific climate states, as this is a crucial piece of landfall risk assessment.

NATALIA ZAKHAROVA 4/10 Goldberg Martinson Menke

Geophysical monitoring of carbon dioxide geological storage in basaltic reservoirs. Minimizing climate change from increasing atmospheric concentrations of carbon dioxide (CO2) requires dramatic reductions in anthropogenic CO2 emissions. A vital strategy is carbon capture and storage (CCS), also called carbon sequestration. Geological storage, which implies injecting CO2 into underground geologic formations, is currently the most mature storage method. Detailed site characterization and reliable monitoring are crucial aspects for successful CO2 geologic storage. My research focuses on applying geophysical methods for these purposes. Although there are successful examples of geophysical monitoring of CO2 plume propagation, quantifying the amount of CO2 underground remains a challenging task. My major goal is to develop viable monitoring techniques using a complex of geophysical methods, such as well logging, petrophysical analysis and seismic surveys. In a number of recent studies, basaltic rocks have been proposed as a promising target for CO2 storage. Unlike sedimentary aquifers, basalts have a high potential for geochemical trapping, which involves long-term reactions of CO2 with host rocks and the formation of stable minerals such as carbonates under in situ conditions. Massive continental flood basalts exist on many continents and

represent a potentially important host medium for CO2 geological sequestration, especially in regions where conventional storage options in sedimentary basins are limited. As a part of my dissertation I am conducting pre-injection reservoir characterization based on well logging data for a pilot CO2 sequestration project in the Columbia River flood basalts (Washington, USA). This project is one of the first field tests specifically designed to confirm the feasibility of permanently and safely sequestering of CO2 within deep flood basalt formations. An accurate petrophysical analysis is crucial for describing reservoir properties and characterizing its storage capacity and containment, as well as for establishing base-line conditions for future post-injection monitoring. One of the greatest challenges will be monitoring of basalt mineralization due to CO2 injection. I am currently investigating the feasibility of applying an innovative approach for mineralization monitoring using borehole elemental spectroscopy measurements and core analysis (including infrared spectroscopy and geochemical data).